The research proposed in this application for a Scientist Development Award (K-21) will contributed to our understanding of how animals learn complex vocalizations. This goal will be accomplished by 1) examining the functional organization of the neutral circuits underlying vocal learning in parakeets, which are small parrots, and 2) comparing these data to what is known about the neural mechanisms of vocal learning in other birds. The ability to learn complex vocalizations has evolved only in humans, oscine songbirds, and parrots. Previous studies on the neural substrates of vocal learning have focused almost entirely on songbirds. Vocal learning in parrots is a better model system for human speech learning, however, because some parrots can actually use the learned vocalizations to communicate meaningfully with humans. Furthermore, vocal learning evolved independently in parrots and songbirds. Therefore, we can derive general rules of how neural systems capable of vocal learning must be constructed by identifying those features of the vocal control system that are similar in parrots and songbirds, and hence due to convergent evolution. By extending the comparison to birds that cannot learn vocalizations, we can reconstruct those evolutionary changes that transformed the vocal control systems from being developmentally rigid to being capable of learning. This knowledge, in turn, will help us to understand the etiology of human behavioral disorders such as autism and schizophrenia, which involve a lack of behavioral plasticity. The basic hypotheses to be examined in the proposed research that the anatomically defined vocal control system in parakeets can be divided into 1) a vocal motor system that directly controls vocalization, and 2) an auditory pathway that provides the vocal motor system with the auditory feedback required for vocal learning. This hypothesis will be tested by a) chemically lesioning specific bran areas and quantifying the effects on vocal behavior, b) recording vocalization-correlated neural activity in freely moving, vocalizing birds. and c) recording auditory responses from neurons in the pathway that is hypothesized to provide the vocal motor system with the auditory feedback required for vocal learning.